Referring to FIG. 1, which shows the palm side of a human hand, it can be seen that the tendons pass into the digits inside a tendon sheath. This sheath functions to keep the synovial fluid around the tendon within the sheath. The synovial fluid lubricates the tendon as it moves back and forth in the digit. The beginning of the sheath, at the base of the digit, is called the A1 pulley. The purpose of the pullies is to keep the tendons close to the bone. As the digit bends, the pullies prevent the tendons from sagging away from the bone. The A1 pulley is the area that is involved in trigger finger or trigger thumb.
It is not known exactly what causes trigger finger or trigger thumb. However, it is generally believed that a contributing factor is impact on the palm of the hand. The tendon is subjected to significant forces at the A1 pulley, where trigger finger or thumb occurs. The tendon swells or forms a nodule at the base of the digit and has difficulty passing through the tendon sheath at the A1 pulley. The result is a painful “popping” or “snapping” of the digit in the palm at the location of the A1 pulley as the swollen part of the tendon passes the A1 pulley. As the condition worsens, the “popping” or “snapping” becomes more frequent. In serious cases, the swelling in the tendon cannot pass the A1 pulley and the digit is locked in position, i.e., it cannot bend or cannot be straightened.
Trigger finger or thumb does not seem to be related to any particular trauma event but, rather, comes on gradually. It typically affects people in their 40's, 50's and 60's and is about two to three times more common in women than in men. It can affect any digit or more than one digit on a hand at the same time or the digits of both hands at the same time. It is not uncommon for patients to be affected in more than one digit. The fourth digit is the digit most often involved.
Trigger finger or thumb is generally treated by splinting and/or steroid injections and/or surgery. Splinting has been found to be minimally effective and then only as long as the splint is worn. However, splints are very much disfavored by patients, are uncomfortable, limit the use of the digit and sometimes the hand and, generally, do not solve the problem of trigger finger or thumb. Multiple steroid injections in the affected digit have been found to be an effective treatment in many instances to resolve the problem of digit locking. However, the treatment is often only effective in the short term and, generally, does not completely resolve the problem of trigger finger or thumb. Approximately fifty percent of patients experiencing trigger finger or thumb go on to surgery. During the surgery, the tendon sheath is cut to allow the tendon to freely pass. The problem with surgery is that many patients recoil at the thought of it and will not have it done, preferring to live with the problem of trigger finger or thumb. Moreover, inherent in every surgery are the risks of anesthesia, infection, failure to relieve the triggering, recurrence of triggering and damage to other structures of the digit or hand.
Accordingly, there is a need for a non-surgical device and technique for the treatment of trigger finger and thumb which is effective in resolving the triggering, comfortable for the patient, easy to use and relatively inexpensive.